An Analysis and Modelling of Spinning Process without Wall-Thickness Reduction

Through the spinning process it is made the different axial-symmetrical parts by acting spinning roller on blank of sheet metal, which is shaped through a chuck. In the paper is shown an analyse of stressed and strained state, as well as forming force components of spinning process. On the ground of experimental results it is made mathematical modelling of spinning forming force. The obtained mathematical model describes enough accurate and reliable (P = 0,98) the spinning forming force

An Analysis and Modelling of Spinning Process without Wall-Thickness Reduction

Through the spinning process it is made the different axial-symmetrical parts by acting spinning roller on blank of sheet metal, which is shaped through a chuck. In the paper is shown an analyse of stressed and strained state, as well as forming force components of spinning process. On the ground of experimental results it is made mathematical modelling of spinning forming force. The obtained mathematical model describes enough accurate and reliable (P = 0,98) the spinning forming force

Pap Smear Adequacy – Is the Assessing Criterion Including Endocervical Cells Really Valid?

The significance of endocervical cylindrical cells (EC) as a criterion of sample adequacy has been established on 1,000 patients by comparing VCE smears (vaginal, cervical, endocervical) with or without EC in relation to prevalence of abnormal cells, prevalence of histological diagnosed lesions and sensitivity and negative predictive value of Pap smear, as well as by comparison of negative findings without EC with control smears with the aim of discovering overlooked lesions. A considerably greater yield of cytological (107/536 in relation to 49/464) and histological (105/536 in relation to 55/464) (p<0.05) abnormalities in smears with EC support the hypothesis that the presence of EC is strongly and positively associated with prevalence of disease. In contrast, the presence of EC predicts only a moderate improvement in Pap smear quality with a weaker effect on sensitivity (95% in relation to 80%). During two-years monitoring of patients with negative Pap smear and negative colposcopy (403 with EC and 390 without EC in smears), no positive cytology/histology diagnosis was made. Also, because the prevalence of missed lesions among negative Pap smears is extremely low in absolute terms, no appreciable impact on negative predictive value was observed (98.8% in relation to 97.3%)

The influence of mechanical properties of workpiece material on the main cutting force in face milling

The paper presents the research into cutting forces in face milling of three different materials: steel Č 4732 (EN42CrMo4), nodular cast iron NL500 (EN-GJS-500-7) and silumine AlSi10Mg (EN AC-AlSi10Mg). Obtained results show that hardness and tensile strength values of workpiece material have a significant influence on the main cutting force, and thereby on the cutting energy in machining

Utjecaj mehaničkih karakteristika materijala obratka na glavnu silu rezanja pri čeonom glodanju

The paper presents the research into cutting forces in face milling of three different materials: steel Č 4732 (EN42CrMo4), nodular cast iron NL500 (EN-GJS-500-7) and silumine AlSi10Mg (EN AC-AlSi10Mg). Obtained results show that hardness and tensile strength values of workpiece material have a significant influence on the main cutting force, and thereby on the cutting energy in machining.U radu su prikazana istraživanja sila rezanja pri čeonom glodanju za tri različita materijala: čelik Č 4732 (EN42CrMo4), nodularni lijev NL500 (EN-GJS-500-7) i silumin AlSi10Mg (EN AC-AlSi10Mg). Dobiveni rezultati pokazuju da vrijednosti tvrdoće i vlačne čvrstoće materijala obratka imaju veliki utjecaj na glavnu silu rezanja, a time i na ukupno utrošenu energiju rezanja pri obradi

Plastično oblikovanje lima nestišljivim fluidom

The plastic forming of sheet metal with fluid pressure has most application at the modern producing of special elements and element of widespread use. Higher relations of drawing ratio are reached by the application of this technology and it is decreased the number of necessary operations and tools as well as the decreasing of costs to product unit. The quality of produced products is considerable better than clasic methods therefore there are satisfactory tribological conditions of plastic forming. Therefore there is considerable application increasing of this technology at the technological developed countries.Plastično oblikovanje pomoću nestišljivog fluida ima sve veću primjenu u modernoj proizvodnji specijalnih elemenata i elemenata široke potrošnje. Primjenom ove tehnologije postižu se veći odnosi izvlačenja, smanjuje se broj potrebnih operacija i alata, te se smanjuju troškovi izrade po jedinici proizvoda. Kvaliteta dobivenih proizvoda je znatno bolja u odnosu na klasične metode jer su bolji tribološki uvjeti plastičnog oblikovanja. Zbog toga je značajan porast primjene ove tehnologije u tehnološki razvijenim zemljama

Cobalt, nickel, wolfram, cadmium, selenium, silver and gold-bearing mercurian tetrahedrite from the Saski Rad barite-siderite deposit in the Mid-Bosnian Schist Mts.

In the Saski Rad barite-siderite ore deposit, Hg-tetrahedrite is the main ore mineral, pyrite and some others are only accessories. Two tetrahedrite samples (fresh and weathered) have been analysed in detail: major and minor components, constituent trace elements, REE, and δ34SCDT values. The following microconstituents have been detected: Ni 71 ppm (in fresh sample) and 70 ppm (in weathered sample); Co 113 and 90 ppm; Cd 27 and 20 ppm; W 20 and 5 ppm, Bi 2500 and 1613 ppm; Se >100 and 72 ppm and Au 11 and 9 ppm. These values have been compared with the only currently available analysis of Hg-tetrahedrite from the Duboki Vagan near Kreševo in the Mid-Bosnian Schist Mts. (MBSM) carried out by JURKOVIĆ et al. (2010): Ni 266.2 ppm; Co 63.5 ppm, Cd 319.6 ppm; Bi 1466.0 ppm; Au 38.96 ppm which also agrees with our analysis of Hg-tetrahedrite from the Brixlegg barite deposit in Tyrol, Austria: Co 234.4 ppm; Cd 160.5 ppm; W 6.7 ppm; Sn 1.0 ppm; Bi 909.1 ppm; Se > 100 ppm and Au 2.3 ppm. The δ34SCDT isotope values of six tetrahedrites from the Saski Rad are on average –10.11‰, those of three tetrahedrites from the Duboki Vagan –10,05‰ and of the tetrahedrite from the Brixlegg deposit –1.60‰. The ΣREE content is lower in two analysed tetrahedrites from the Saski Rad deposit (10 ppm) compared to the tetrahedrite from Duboki Vagan (15 ppm) and the tetrahedrite from Brixlegg (17.4 ppm). The analysed barite sample from the Saski Rad deposit does not contain microconstituents typical of Hg-tetrahedrite. The distribution and genetic signifi cance of some trace elements, tetrahedrite microconstituents, REE and siderite isomorphic components in the seven most important genetic and paragenetic types of ore deposits in the MBSM and South-Eastern Bosnia have been commented upon.</p

Physical modelling and numerical finite element method (FEM) simulation of forging in open die of alloy AIMgSi0,5

This paper researches the process of forging in open die of gradual axial-symmetric workpiece made of alloy AIMg-Si0,5. The physical modelling was carried out, for which an original method for physical discretisation and numerical FEM analysis was developed. The components of tensor were determined: strain, strain rate, stress and the corresponding effective parameters. The results obtained experimentally and through a numerical FEM simulation were compared and analysed

A Zincian Chrome-Spinel from the Cr-Ba-Fe-Cu-Zn Deposit near Busovaca (Bosnia and Herzegovina)

The metamorphic complex of the Busovaca area is mostly composed of Upper Silurian-Lower Devonian metapelites, metapsammites and metarhyolites formed under low grade metamorphism at 350° to 450°C and 3 to 5 kbars. The ore minerals of the Busovaca deposit are: magnetite (with relics of zincian chrome-spinel), rimmed by ferrichromite, and pyrite, chalcopyrite, enargite, bornite and siegenite. The gangue minerals are: siderite, quartz, albite, hyalophane, muscovite, chromian-chlorite and manganoan ankerite. Proton microprobe analyses (PIXE) were made of samples A (core Ac of the slightly altered chrome-spinel), B (strongly altered chrome-spinel with Bc-core, Bfc-ferrichromite zones, Br-magnetite rim) and C (cryptically zoned magnetite with Cc-core and Cr-magnetite rim). The results are recalculated in formulae, and presented on separate diagrams. The optical investigations, microprobe analyses, beam-scan photographs, diffusion rates of Mg, Al, Zn, Cr, and Mn, and diagrams, allow the following conclusions to be made: (1) magmatic origin of the primary chrome-spinel, (2) the emplacement of the Zn was prior to the alteration under very low f02, most probably synchronous with the sulphide mineralization; (3) the alteration process took place in two phases: (a) the early stage volume-for-volume replacement and formation of the ferrichromite and magnetite zones, (b) the late stage characterized by decolourization and/or resorption, and/or dissolution of the core (patches, specks, “atoll structure”); (4) released Al, Cr, Mn, and Zn have been taken up by silicate, carbonate and oxide minerals forming chromian-chlorite, manganoan ankerite or contaminated siderite and pyrite; (5) the diffusion rates among Al, Zn, Cr, and Mn during different stages of the alteration have the following sequence: Al - Zn - Cr - Mn; (6) the optically unzoned magnetite crystals or aggregates originated in chrome-spinel; (7) the mineral assemblage of the Busovaca deposit co-exists with the surrounding metamorphic complex belonging to the greenschist facies

Influece of the austempering temperature on the tensile strength of the austempered ductile iron (ADI) samples

Austempered Ductile Iron (ADI) is a class of ductile iron subjected to a two-step heat treatment process – austenitization and austempering. The heat treatment gives to ADI a high value of tensile strength and an especially good strength-to-weight ratio. However, designers in most cases are unfamiliar with this material that can compete favorably with steel and aluminum castings, weldments and forgings. The high tensile strength of ADI is the result of its unique ausferrite microstructure. In this paper, an investigation of the influence of the austempering temperature on the tensile strength of the ADI samples is presented